Reduction of infection after cardiac surgery: a clinical trial

Sternal reconstruction after post-sternotomy mediastinitis

Background

Deep sternal wound complications are uncommon after cardiac surgery. They comprise sternal dehiscence, deep sternal wound infections and mediastinitis, which will be treated as varying expressions of a singular pathology for reasons explained in the text.

Methodology and review

This article reviews the definition, prevalence, risk factors, prevention, diagnosis, microbiology and management of deep sternal wound infections and mediastinitis after cardiac surgery. The role of negative pressure wound therapy and initial and delayed surgical management is discussed with special emphasis on plastic techniques with muscle and omental flaps. Recent advances in reconstructive surgery are presented.

Conclusions

Deep sternal wound complications no longer spell debilitating morbidity and high mortality. Better understanding of risk factors that predispose to deep sternal wound complications and general improvement in theatre protocols for asepsis have dramatically reduced the incidence of deep sternal wound complications. Negative pressure wound therapy and appropriately timed and staged muscle or omental flap reconstruction have transformed the outcomes once these complications occur.

Analysis of risk factors for sternal surgical site infection: emphasizing the appropriate ventilation of the operating theaters

OBJECTIVE

To determine the incidence of and identify risk factors for sternal surgical site infection (SSI).

DESIGN

Prospective cohort study. Data on potential risk factors, including the type of operating theater and infection data, were collected prospectively and analyzed by multivariate analysis.

SETTING

Siyami Ersek Thoracic and Cardiovascular Surgery Hospital, a 700-bed teaching hospital and the largest center for cardiac surgery in Turkey. The cardiothoracic unit performs approximately 3,000 cardiac operations per year.

PATIENTS

All adult patients who underwent cardiac surgery with sternotomy between January 14, 2002, and July 1, 2002, and who survived at least 4 days after surgery were included in the study.

RESULTS

Potential risk factor data were complete for 991 patients. There was sternal SSI in 41 patients (4.1%). Female sex, diabetes mellitus, operation performed in the older operating theaters, and duration of procedure exceeding 5 hours were identified as independent risk factors for sternal SSI.

CONCLUSIONS

Female and diabetic patients are at higher risk for sternal SSI and should be followed up carefully after cardiac surgery to prevent the development of sternal SSI. Reducing the duration of surgery could reduce the rate of postoperative sternal SSI. The operating theater environment may have an important role in the pathogenesis of sternal SSI, and appropriate ventilation of the operating theaters would be critical in the prevention of sternal SSI.

A Steel Band in Addition to 8 Wire Cerclages Reduces the Risk of Sternal Dehiscence after Median Sternotomy

BACKGROUND

Sternal dehiscence after full median sternotomy may result in wound-healing disorders, including osteomyelitis. The consequences are extended hospitalization, plastic surgery, stress for the patient, and increased costs. Stable closure of the median sternotomy plays a crucial role in the avoidance of sternal dehiscence and osteomyelitis.

METHODS

All patients who underwent full sternotomy from January 1999 until December 2001 were investigated with respect to the incidence of sternal dehiscence. Since January 2000, patients supposed to be at risk for sternum dehiscence were more frequently treated with an Ethicon steel band at the third intercostal space in addition to standard osteosynthesis with 8 wire cerclages.

RESULTS

Since the introduction of this method, the incidences of sternal dehiscence and sternal wound infections decreased from 2.9% and 0.9 %, respectively, in 1999 to 0.3% and 0.2%, respectively, in 2001. This decline resulted in shorter postoperative hospital stays, less stress for the patients, and substantial reductions in postsurgical costs.

CONCLUSIONS

A steel band used in addition to standard osteosynthesis with 8 wire cerclages is a safe and effective procedure resulting in a statistically significant decrease in the frequency of sternal dehiscence.

Suppurative mediastinitis after open-heart surgery: a comparison between cases caused by Gram-negative rods and by Gram-positive cocci

OBJECTIVE: To compare clinical characteristics and risk factors of suppurative postsurgical mediastinitis according to its etiology. METHODS: Suppurative postsurgical mediastinitis developed in 45 (2.5%) of 1779 patients who underwent open-heart surgery at the Hospital Virgen del Rocío in Seville, Spain, from 1986 to 1996. Microbiological diagnosis was available in 42 patients. RESULTS: Gram-negative rods were isolated in 19 cases and Gram-positive cocci in 23 cases. Seventeen isolates (38%) were sensitive to the antimicrobial agent used perioperatively. Patients with Gram-negative rod infection had a longer duration of bypass (127plus minus36 min versus 96plus minus34 min, p<0.01), and a worse postoperative condition. Longer mechanical ventilation (4plus minus7 days versus 1plus minus2 days, p<0.05) and concomitant infection in a remote site (pulmonary and/or urinary infection) were more frequently observed in this group than in patients with Gram-positive infections (58% versus 22%, p<0.05). Twenty patients (51%) were bacteremic. The mortality rate was 20% (five of 45). CONCLUSIONS: Preventable postoperative remote-site infection may lead to mediastinitis, especially if Gram-negative rods are involved.

Operating theatre ventilation standards and the risk of postoperative infection

Some form of specialized ventilation has been a feature of operating theatres for over 60 years, and ultraclean ventilation has been shown to reduce postoperative infection after prosthetic joint surgery. However, controversy remains over the contribution of plenum (conventional) ventilation to the prevention of infection after surgery in which there is no prosthetic implant. A previous survey in Great Britain and Ireland indicated the continued use of non-ventilated theatres for minor surgery. Laparoscopic and other forms of minimally invasive surgery (MIS) have become more common in the last decade, and offer the advantages of reduced morbidity and shorter hospital stay. However, it is not clear whether such surgery requires the same standard of ventilation facilities as open surgery and, in particular, whether all MIS procedures should be performed in a plenum-ventilated theatre. Furthermore, there are many diagnostic and therapeutic procedures currently performed in cardiac and radiology departments where only natural ventilation is available. The Hospital Infection Society (HIS) Working Party on Infection Control and Operating Theatres is attempting to assess the ventilation facilities currently utilized for a wide variety of MIS procedures. This review should form the basis of future HIS guidance on minimum standards in this area.

Handwashing before entering the intensive care unit: what we learned from continuous video-camera surveillance

Handwashing is one of the most important factors in controlling the spread of bacteria and in preventing the development of infections. This simple procedure does not have a high compliance rate. The Association for Professionals in Infection Control and Epidemiology, Inc, guideline recommends that hands must be washed before and after patient contact. In our intensive care unit (ICU), we have made it a rule that everyone should wash their hands before entering the ICU. The purpose of this study was to ascertain the handwashing compliance of all personnel and visitors to the ICU. A ceiling-mounted video camera connected to a time-lapse video cassette recorder recorded each person's actions when they entered the ICU during a 7-day period. Handwashing compliance was assessed for 3 different categories: ICU personnel, non-ICU personnel, and visitors to patients. There were 1030 entries to the ICU during the observation period. ICU personnel complied with handwashing in 71% of entries, non-ICU personnel in 74% of entries, and visitors to patients in 94% of entries. Handwashing compliance by visitors to patients was significantly higher than among personnel (P <.001). Handwashing compliance among personnel before entering the ICU was low. Continuous effort is needed to raise awareness of the handwashing issue, not only to ensure compliance with APIC recommendations but also in our facility, to ensure that health care personnel wash their hands on entry to the ICU.

Results of a comprehensive infection control program for reducing surgical-site infections in coronary artery bypass surgery

OBJECTIVE

To evaluate the efficacy of a comprehensive infection control program on the reduction of surgical-site infections (SSIs) following coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective cohort study.

SETTING

1,000-bed tertiary-care hospital.

PATIENTS

Persons undergoing CABG with or without concomitant valve surgery from April 1991 through December 1994.

INTERVENTIONS

Prospective surveillance, quarterly reporting of SSI rates, chlorhexidene showers, discontinuation of shaving, administration of antibiotic prophylaxis in the holding area, elimination of ice baths for cooling of cardioplegia solution, limitation of operating room traffic, minimization of flash sterilization, and elimination of postoperative tap-water wound bathing for 96 hours. Logistic regression models were fitted to assess infection rates over time, adjusting for severity of illness, surgeon, patient characteristics, and type of surgery.

RESULTS

2,231 procedures were performed. A reduction in infection rates was noted at all sites. The rate of deep chest infections decreased from 2.6% in 1991 to 1.6% in 1994. Over the same period, the rate of leg infections decreased from 6.8% to 2.7%, and of all SSI from 12.4% to 8.9%. The adjusted odds ratio (OR) for all SSIs for the end of 1994 compared to December 31, 1991, was 0.37 (95% confidence interval [CI95], 0.22-0.63). For deep chest and mediastinal infections, the adjusted OR comparing the same period was 0.69 (CI95, 0.28-1.71).

CONCLUSIONS

We observed significant reductions in SSI rates of deep and superficial sites in CABG surgery following implementation of a comprehensive infection control program. These differences remained significant when adjusted for potential confounding covariables.

Is mediastinitis a preventable complication? A 10-year review

BACKGROUND

The incidence of mediastinitis after cardiac surgical intervention is reported to be between 0.15% and 5% and is a major cause of postoperative morbidity. A number of risk factors have been identified, most of which are not modifiable. It is our contention that this complication can be reduced to a minimum by the consistent application of good operative technique and postoperative management.

METHODS

We reviewed the records of all 9,771 patients who underwent cardiac surgical procedures between 1987 and 1997. All operations were performed using a common skin preparation, draping, and antibiotic prophylaxis. Cases of mediastinitis were defined according to Centers for Disease Control and Prevention criteria and were identified from three sources: medical records database, hospital infection control, and the Society of Thoracic Surgeons database. Risk factors were assessed using chi2 and Fisher's exact tests.

RESULTS

Of 24 patients identified as having deep sternal wound infection (incidence, 0.25%), 2 died (mortality rate, 8.3%), 18 required reoperation (75%), and only 4 needed pectoral muscle flaps. Statistical analysis revealed only the presence of chronic obstructive pulmonary disease as a significant risk factor (p < 0.01). Other factors, including diabetes, renal failure, smoking, sex, age, reoperation, morbid obesity, and steroid use, were not significant. The use of internal mammary arteries (single or bilateral) was not associated with mediastinitis. Postoperative complications, including prolonged ventilation, inotropic support, and the need for blood products, were not significant risk factors. The patients who developed mediastinitis were more likely to be readmitted to the hospital (p < 0.005) and more likely to require reoperation (p < 0.005).

CONCLUSIONS

In a large patient series we found a low incidence of mediastinitis (0.25%) and an even lower incidence of required reoperation (0.19%). Except for the use of bone wax and the use of bilateral mammary arteries in diabetic patients, none of the previously identified risk factors are modifiable. We believe that with strict adherence to perioperative aseptic technique, attention to hemostasis, and precise sternal closure, a very low incidence of mediastinitis can be achieved.

Secular trends in nosocomial bloodstream infections in a 55-bed cardiothoracic intensive care unit

BACKGROUND

Although bloodstream infections (BSIs) occur more frequently in intensive care unit patients than in ward patients, most studies of nosocomial BSIs in critically ill patients have not distinguished between intensive care unit populations beyond surgical, medical, and pediatric patients.

METHODS

The primary objective of this study was to characterize the secular trends in rates of nosocomial BSIs for all pathogens among patients admitted to a busy cardiothoracic intensive care unit in a single tertiary care institution between January 1986 and December 1995. Patients with nosocomial BSIs were identified through continual prospective surveillance.

RESULTS

A total of 40,207 patients were admitted to the cardiothoracic intensive care unit during the 10-year study period, and 804 episodes of nosocomial BSIs among 681 patients were identified. The mean crude BSI infection rate was 6.0 per 1,000 patient-care days and increased linearly during the study period (range, 4.4 to 8.1 per 1000 patient-care days), and approached statistical significance (p value = 0.07). The most common organisms causing BSIs were Staphylococcus aureus (12%), coagulase-negative staphylococci (11%), Candida albicans (11%), Pseudomonas aeruginosa (10%), and Enterococci (9%). The leading sources of nosocomial BSIs were primary BSIs (33%), intravascular devices (27%), lower respiratory tract infections (17%), and surgical wound infections (12%). The etiologic fraction or the proportion of deaths in cardiothoracic intensive care unit patients with BSIs was 15-fold higher than those patients without BSIs (37% versus 2.5%, p < 0.001).

CONCLUSIONS

Rates of nosocomial BSIs among patients in our cardiothoracic intensive care unit have increased linearly during the past decade and patients with nosocomial BSIs have an increased risk of in hospital mortality.

Poststernotomy mediastinitis treated by transposition of the greater omentum

Due to its anatomical structure and physiological properties, omental tissue has proven to be beneficial when transposed to the thorax to treat severe mediastinal infections. Between April 1987 and July 1994, 17,005 open heart operations were performed at our institution. One hundred and forty patients who developed mediastinitis or serious wound infections postoperatively were treated by transposition of the greater omentum into the retrosternal space. These patients were compared with a control group of 100 patients operated in the same period, who did not develop infectious complications postoperatively. Significant differences were found in several risk factors, such as obesity, type, and duration of primary operation, ejection fraction < 30% (< 0.01), as well as the incidence of low cardiac output syndrome treated by insertion of an intra-aortic balloon pump (p < 0.05). However, no significant differences were observed in factors such as diabetes mellitus, emergency operation, reoperation, degree of postoperative bleeding, and duration of aortic cross-clamp time. The mortality of mediastinitis largely depended on the type of primary operation. It was 19.2% in patients who underwent coronary surgery, and 52.2% in patients who underwent transplantation (overall mortality 35.7%). Only in 2% of the patients did we find complications related to the creation of the omental pedicle and its translocation. Today, serious disturbances in sternal wound healing, especially involving mediastinitis, are rare complications in cardiac surgery. Nevertheless, they continue to be associated with high mortality and prolonged hospitalization.

Antibiotic prophylaxis for cardiac surgery: current United Kingdom practice

A questionnaire was sent to 120 United Kingdom cardiac surgeons to ask for information on their use of prophylactic antibiotics in adult cardiac surgical patients. Data on type and duration of antibiotic were specifically sought. The response rate was 91%. All respondents used prophylactic antibiotics: 32% used single agents (second and third generation cephalosporins were the most commonly used) and 68% used either two (89%) or three (11%) antibiotics in combination. The total duration of prophylactic antibiotic treatment was less than 48 hours for 89% of respondents. Single dose antibiotics were used by only 6%. The use of prophylactic antibiotics has changed in the past few years, with a trend away from combinations of antibiotics to single agents. The duration of use of antibiotics has shortened and the use of single dose agents has increased.

Management of deep sternal wound infection after cardiac surgery--Hanuman syndrome

Deep sternal wound infection following open-heart surgery caused sternal osteitis in eight patients and mediastinitis in 27 during 1980-1989. The incidence of such infection was 0.5%. Infection was more common during the last 2 years than in 1980-1987 (0.8% vs. 0.4%), and when bilateral internal mammary artery grafts were dissected (3.2% vs. 0.6% when only one internal mammary artery was used). Cure of mediastinitis was achieved by primary closed irrigation in four of 13 patients and by primary open treatment in five of ten. Muscle flap was employed in totally ten patients and omentum in four before final elimination of infection. Of the 27 patients with mediastinitis, eight (30%) died in the post-operative period of cardiac failure (3 cases), disseminated infection (2), bleeding (2) or aspiration (1). The 5-year survival rate was 43%. Prosthetic value endocarditis caused one late death and necessitated one reoperation. If eradication of postoperative mediastinitis is not achieved by early diagnosis, debridement and closed irrigation, transposition of muscle or omentum should be considered.

Antimicrobial prophylaxis for open heart operations

Between 1986 and 1988, 450 adults undergoing coronary artery bypass, cardiac valve replacement, or both were enrolled into a prospective, randomized, comparative trial of cephalothin versus cefamandole as perioperative prophylaxis. They were assessed during their hospitalization and at 6 weeks and 6 months after discharge for postoperative infectious complications. Eleven patients had major postoperative infections including 5 with sternal wound infections (three bacteremic), 6 with bacteremia, 1 with prosthetic valve endocarditis, and 3 with severe venous donor graft site infections. Eight major infections occurred in patients receiving cephalothin prophylaxis and three in patients receiving cefamandole, with all five sternal wound infections occurring in the cephalothin group. Postoperative pathogens responsible for the major infections included gram-negative aerobes in 5 patients, Staphylococcus aureus in 4, and Staphylococcus epidermidis in 2. Preoperative colonizing staphylococcal isolates were not predictive of postoperative staphylococcal pathogens. Although there was no statistically significant difference in rate of major postoperative infectious complications using either cephalothin or cefamandole prophylaxis, there was a trend in favor of cefamandole. Gram-negative aerobes are becoming increasingly important pathogens in this setting.

Bacteremia and sternal infection after coronary artery bypass grafting

Sternal wound infection remains a source of substantial morbidity and mortality after coronary artery bypass grafting. We noted an association between bacteremias and sternal wound complications in these patients. A review of 835 consecutive coronary bypass patients showed a 3.2% incidence of bacteremia and a 1.9% incidence of deep and superficial sternal wound infection. The sternal wound was the most common source of bacteremia, accounting for 59% of the infections. Coagulase-negative Staphylococcus was responsible for one half of the sternal wound infections. Often, a positive blood culture was the first manifestation of wound infection, occurring before local signs were manifest. We recommend multiple blood cultures in postoperative coronary bypass patients with pronounced fever. If no source of infection can be identified, sternal wound aspirate may be revealing. Appropriate early wound management can then be carried out, maximizing chances for good recovery.